Results of operation and utilization of the Dalat Nuclear Research Reactor
Nuclear Science and Technology, Vol. 4, No. 1 (2014), pp. 01-09
Results of Operation and Utilization of
the Dalat Nuclear Research Reactor
Nguyen Nhi Dien, Luong Ba Vien, Le Vinh Vinh, Duong Van Dong,
Nguyen Xuan Hai, Pham Ngoc Son, Cao Dong Vu
Nuclear Research Institute (NRI), Vietnam Atomic Energy Institute (VINATOM)
01 Nguyen Tu Luc, Dalat, Vietnam
(Received 5 March 2014, accepted 26 March 2014)
Abstract: The Dalat Nuclear Research Reactor (DNRR) with the nominal power of 500 kW was
reconstructed and upgraded from the USA 250-kW TRIGA Mark-II reactor built in early 1960s. The
renovated reactor was put into operation on 20th March 1984. It was designed for the purposes of
radioisotope production (RI), neutron activation analysis (NAA), basic and applied researches, and
nuclear education and training. During the last 30 years of operation, the DNRR was efficiently
utilized for producing many kinds of radioisotopes and radiopharmaceuticals used in nuclear medicine
centers and other users in industry, agriculture, hydrology and scientific research; developing a
combination of nuclear analysis techniques (INAA, RNAA, PGNAA) and physic-chemical methods
for quantitative analysis of about 70 elements and constituents in various samples; carrying out
experiments on the reactor horizontal beam tubes for nuclear data measurement, neutron radiography
and nuclear structure study; and establishing nuclear training and education programs for human
resource development. This paper presents the results of operation and utilization of the DNRR. In
addition, some main reactor renovation projects carried out during the last 10 years are also mentioned
in the paper.
Keywords: DNRR, HEU, LEU, RRRFR, RERTR, WWR-M2, NAA, INAA, RNAA, PGNAA.
I. INTRODUCTION
converted from HEU to Low Enriched
Uranium (LEU) with 19.75% enrichment in
September 2007. Then, the full core conversion
of the reactor to LEU fuel was also performed
from 24th November 2011 to 13th January 2012.
Recently, the DNRR has been operated with a
core configuration loaded with 92 WWR-M2
LEU fuel assemblies and 12 beryllium rods
around the neutron trap.
The DNRR is a 500-kW pool-type
reactor loaded with the Soviet WWR-M2 fuel
assemblies. It was reconstructed and upgraded
from the USA 250-kW TRIGA Mark-II reactor
built in early 1960s. The first criticality of the
renovated reactor was on the 1st November
1983 and its regular operation at nominal
power of 500 kW has been since March 1984.
The first fresh core was loaded with 88 fuel
assemblies enriched to 36% (HEU- Highly
Enriched Uranium).
The reactor is used as a neutron source
for the purposes of radioisotopes production,
neutron activation analysis, basic and applied
researches and training. As a unique research
reactor in Vietnam, the DNRR has been
playing an important role in the research and
development of nuclear technique applications
as well as in nuclear power programme
development of the country. Safe operation and
In the framework of the program on
Russian Research Reactor Fuel Return
(RRRFR) and the program on Reduced
Enrichment for Research and Test Reactor
(RERTR), the DNRR core was partly
©2014 Vietnam Atomic Energy Society and Vietnam Atomic Energy Institute
RESULTS OF OPERATION AND UTILIZATION OF THE DALAT NUCLEAR RESEARCH REACTOR
effective utilization of the reactor expected at
least to the year 2030 are a long-term objective
of the DNRR. For this reason, so far the
Government has strongly supported for many
specific projects in order to upgrade the facility
and improve its operation and utilization.
some main reactor renovation projects carried
out during the last 10 years are also
mentioned, too.
II. BRIEF REACTOR DESCRIPTION
AND IT’S OPERATION
The results of operation and utilization
Main specifications of the DNRR are
shown in Table I.
of the DNRR are presented in this paper and
Table I. Specifications of the DNRR.
Reactor type
Swimming pool TRIGA Mark II, modified to Russian
type of IVV-9
Nominal thermal power
Coolant and moderator
Core cooling mechanism
Reflector
500 kW, steady state
Light water
Natural convection
Beryllium and graphite
Fuel types
WWR-M2, dispersed UO2-Al with 19.75% enrichment,
aluminium cladding
Number of control rods
Materials of control rods
7 (2 safety rods, 4 shim rods, 1 regulating rod)
B4C for safety and shim rods, stainless steel for
automatic regulating rod
Neutron measuring channels
Vertical irradiation channels
6 combined in 3 housings with 1 CFC and 1 CIC each
4 (neutron trap, 1 wet channel, 2 dry channels) and 40
holes at the rotary rack
Horizontal beam-ports
Thermal column
4 (1 tangential - No #3 and 3 radial - No #1, #2, #4)
1
Maximum thermal neutron
flux
2.1x1013 n.cm-2.s-1 (in the neutron trap at core center)
Main utilizations
RI, NAA, PGNAA, NR, basic and applied researches,
nuclear training
The reactor consists of a cylindrical
aluminum tank 6.26 m high and 1.98 m in
diameter of the original TRIGA Mark II
reactor. The reactor core, positioned inside the
graphite reflector, is suspended from above by
an inner cylindrical extracting well so as to
increase the cooling efficiency for copping
with higher thermal power of the reactor. The
vertical section view of the reactor is shown in
Fig. 1 and the cross-section view of the reactor
core is shown in Fig. 2.
2
NGUYEN NHI DIEN et al.
~ 2000 mm
Rotating top lid
SR
Pool tank
Sh
Sh
Upper
cylindrical
shell
~ 6840 mm
Extracting
well
RgR
Concrete
shielding
Spent fuel
storage tank
Thermal
column door
Sh
Sh
A
Graphite
Door plug
Core
SR
(ex bulk-shielding
experimental tank)
Fig. 1. Vertical section view of the DNRR reactor.
Fig. 2. Cross-section view of the core with 92
fuel assemblies.
The reactor core has a cylindrical shape
with a height of 60 cm and a diameter of 44.2
cm, that is constituted of 92 LEU fuel
assemblies, 7 control rods, a neutron trap at the
core center and 3 in-core irradiation facilities.
At present, the DNRR is operated
mainly in continuous runs of 100 or 130 hrs,
once every 3-4 weeks, for radioisotope
production, neutron activation analyses, basic
and applied researches and training. The
remaining time between two consecutive runs
is devoted to maintenance activities and also to
physics experiments. From the first start-up to
the end of 2013, it totaled about 37,800 hrs of
operation, namely a yearly average of 1300
hrs, and the total energy released was about
760 MWd. Detailed yearly operation time of
the DNRR is given in Fig. 3.
Type of fuel with a 235U enrichment of
19.75% of UO2+Al covered by aluminum
cladding is used. Each LEU fuel assembly
contains about 50.5 g of U-235, distributed on
three coaxial fuel tubes, of which the outermost
one is hexagonal shaped and the two inner ones
are circular.
Fig. 3. Yearly operation time of the DNRR.
3
RESULTS OF OPERATION AND UTILIZATION OF THE DALAT NUCLEAR RESEARCH REACTOR
So far, the reactor has proved to be safe
and reliable, as it has never suffered from any
incident, which significantly affected the
environment, and annual operation schedules
have been rigorously respected. The
unscheduled shutdowns were mainly due to
unstable working of the city electric network.
disease therapeutics and 32P in injectable
solution, 99mTc generator of gel type by 98Mo(n,
)99Mo reaction have regularly been produced
and supplied once every 2 weeks. Other
radioisotopes as 51Cr, 60Co, 65Zn, 64Cu, 24Na,
etc. were also produced in a small amount
when requested. 53Sm in solution form was
ready for labelling. Totally, about 5,500 Ci of
radioisotopes have been produced and supplied
to medical uses so far with a yearly average in
the last 5 years of about 400 Ci (Fig. 4)
correspondingly.
III. MAIN RESULTS OF REACTOR
UTILIZATION
A. Radioisotopes and radiopharmaceuticals
production
In order to support the application of
Research
on
radioisotope
production
and
53
99mTc, 113mIn and Sm radioisotopes in clinical
radiopharmaceutical
serving
diagnosis and therapeutics, the preparation of
radio-pharmaceuticals in Kit form for labelling
was carried out in parallel with the
development of 99mTc generator systems.
About 17 labeled compounds kits have been
regularly prepared and supplied including
Phytate, Gluconate, Pyrophosphate, Citrate,
DMSA, HIDA, DTPA, Macroaggregated HSA
and EHDP, etc.. The annual production rate is
about 1000 bottles for each Kit which is
equivalent to 5000 diagnostic doses.
nuclear medicine and other users such as
industry, agriculture, hydrology, scientific
research, etc. is oriented towards efficient use
of the reactor. Via such research a variety of
products including 131I, 32P applicators and
solutions, 99mTc generators, etc. were produced.
For medicine applications, radioisotopes
and radiopharmaceuticals have been delivered
to 25 hospitals throughout the country. The
main radioisotopes, such as 131I in NaI solution
and 131I capsule type, 32P applicators for skin
Fig. 4. Total radioactivity of RI produced annually at Dalat Nuclear Research
4
NGUYEN NHI DIEN et al.
Other applications of radioisotopes
channel. An auto-pneumatic transfer system
installed in 2012 at the DNRR can transfer a
sample from irradiation position to measuring
detector about 3 seconds.
produced at the DNRR are radiotracer
technique in sediment studies, oil exploitation,
chemical industry, biology, agriculture and
46
hydrology. Some main products are Sc, 192Ir,
The k-zero method for INAA has been
also developed to analyse airborne particulate
samples for investigation of air pollution; crude
oil samples and base rock samples for oil field
study. Based on developed k-zero-INAA
method, a multi-elements analysis procedures
have been applied to simultaneously determine
concentration for about 31 elements including
Al, As, Ba, Br, Ca, Cl, Cr, Cu, Dy, Eu, Fe, Ga,
Hf, Ho, K, La, Lu, Mg, Mn, Na, Sb, Sc, Sm,
Sr, Th, Ti, V, Yb, Zn.
198Au, 131I, 140La, etc. In addition, some small
sources of 192Ir and 60Co with low radioactivity
have also been produced for industry
applications.
B. Neutron activation analysis
Research on analytical techniques based
on neutron activation and other related
processes consists of the elaboration of
analytical processes and the design and
construction of analytical instruments.
C. Neutron beam utilization
Requests of many branches of the
national economy for various types of samples
have quickly been responded. NAA at the
DNRR has always been met the demand of
analytical services for geology exploration, oil
The reactor has four horizontal beam
ports, which provide beams of neutron and
gamma radiation for a variety of experiments.
They also provide irradiation facilities for
large specimens in a region close to the
reactor core. Besides, the reactor also has a
large thermal column with outside dimensions
of 1.2m by 1.2m in cross section and 1.6m in
length (Fig. 5).
prospecting,
agriculture,
biology,
environmental studies, etc.
The relatively high neutron flux in
irradiation channels of the reactor allows
elemental analysis using various neutron
activation approaches, such as Instrumental
NAA (INAA), Radiochemical NAA (RNAA),
Delayed NAA (DNAA) and Prompt gamma
NAA (PGNAA). By the end of 2013, a total
of about 60,000 samples have been irradiated
at the reactor with a yearly average of 2000
samples. It can be estimated that those make
up 60% of geological samples, 10% of
biological samples, 20% of environmental
samples, 5% of soil and agriculture materials,
3% of industrial materials.
Up to now, only three beam ports (No.2,
No.3 and No.4) and the thermal column have
been used for reseaches and applications. At
the beam port No.2, a BGO-HPGe gamma-rays
Compton suppression spectrometer has been
recently
installed
for
PGNAA
and
experimental researches on neutron capture
reactions. The filtered thermal neutron beams
extracted from the tangential beam port No.3
are used for nuclear structure studies,
especially for experimental determination of
nuclear energy levels and level density in
regions below neutron binding energy. The
filtered neutron beams at the piercing beam
port No.4 with quasi-monoenergies of 24keV,
54keV, 59keV, 133keV and 148keV are used
In order to determine the elements
having short-lived radionuclides, the method of
cyclic INAA with the alternation of irradiation
and measurement was implemented by using
the thermal column and vertical irradiation
5
RESULTS OF OPERATION AND UTILIZATION OF THE DALAT NUCLEAR RESEARCH REACTOR
for the mesurements of neutron total and
capture cross sections. In addition, these
neutron beams are also applied for practical
study on radiation shielding design. Typical
research activities using neutron beam of the
DNRR are listed below.
Thermal column
No. 2: Gamma spectrometry
system with BGO detector for
PGNAA and neutron capture
reactions study
No. 3: Nuclear
structure study
Column
door
Beam port # 2
Beam port # 3
Thermal
Column
Stainless steel
Aluminum
Graphite reflector
Pool tank wall
Core
Bellow s
assembly
Beam port # 1
Beam port # 4
No. 4: Nuclear data
measurement
Thermalizing column (closed)
This port is closed
Concrete
shielding
Spent fuel storage tank
Fig. 5. Horizontal section view of the DNRR.
Neutron physics and nuclear data measurement
- Measurement of isomeric ratio created
in the reaction 81Br(n, )82Br on the 55 keV and
144 keV neutron beams;
In the keV energy region, filtered
neutron beams are the most intense sources,
which can be used to obtain neutron data for
reactors and other applications. The following
experiments have been carried out at the
DNRR including:
- And other investigations, such as
average resonance capture measurements,
using the - coincidence spectrometer for
study on the (n, 2) reaction, etc.
Application of neutron capture gamma ray
spectroscopy
- Total neutron cross section measurement
for 238U, Fe, Al, Pb on filtered neutron beams
at 144 keV, 55 keV, 25 keV and evaluation of
average neutron resonance parameters from
experimental data;
- Development of PGNAA technique using
the filtered thermal neutron beam in
combination with the Compton-suppressed
spectrometer for analyzing Fe, Co, Ni, C in
steel samples; Si, Ca, Fe, Al in cement
samples; Gd, Sm, Nd in uranium ores, Sm, Gd
in rare earth ores; etc.;
- Gamma ray spectra measurement from
neutron capture reaction of some reactor
materials (Al, Fe, Be, etc.) on filtered neutron
beam at 55 keV and 144 keV;
- Utilization of the PGNAA method for
investigating the correlation between boron
and tin concentrations in geological samples as
a geochemical indication in exploration and
assessment of natural mineral resources;
analyzing boron in sediment and sand samples
-
Measurement of average neutron
radioactive capture cross section of 238U, 98Mo,
151Eu, 153Eu on the 55 keV and 144 keV
neutron beams;
6
NGUYEN NHI DIEN et al.
to complement reference data for such samples
from rivers;
Besides, the DNRR has been used as a
main tool for practical training, a set of
equipment was supported under IAEA TC
project, bilateral projects with the Japan
Atomic Energy Agency and Bhabha Atomic
Research Center of India. The measuring
systems for practices at the Training Center
can meet the fast increasing demand and is
expected to move forward to the regional
standard in the field of nuclear training.
- Development of the spectrometer of
summation of amplitudes of coinciding pulses
for (n, 2) reaction research and for measuring
activity of activated elements with high
possibility of cascade transitions.
D. Eduacation and training activities
Training Center at Dalat Nuclear
Research Institute which was established in
1999 is responsible for organizing training
courses and training in reactor engineering,
nuclear and radiation safety, application of
nuclear techniques and radioisotopes in
industry, agriculture, biology and environment,
etc. Training courses on non-destructive
evaluation (NDE) including radiographic
testing, ultrasonic testing as well as on security
of nuclear facilities and radiation sources have
also been done. The center also is the training
facility for expertise students from local
universities and foreign postgraduate students.
Thereby, the human resource development is
conducted annually so that it can deal with
scientific works of higher and higher quality
and meet a huge demand in the field of nuclear
science and technology in Vietnam in the
future. Thanks to the bilateral co-operation
with the Japan Atomic Energy Agency, US
Department of Energy, Bhabha Atomic
Research Center of India, and Korea Atomic
Energy Research Institute, we have conducted
a variety of training courses in the four
following key areas:
E. Other applications
Research on sediment using radiotracer
techniques was carried out to investigate bed
load layers displacement at estuaries
navigation channel region and to explain the
sediment deposition phenomenon causing
frequent dredging activities.
Research on radio-biology consists of
using gamma radiation associated with other
factors for improving agricultural seeds and
applying radioactive tracers for studying
biological metabolism, especially nutrition
problems. These studies are to investigate
phosphorus absorption and other nutritional
problems during the growing processes of rice
and other plants. Irradiation effects on some
plants to gain higher yield or environment
adapted varieties were also studied.
Gemstone colorizing experiments of
topaz and sapphire in the reactor core, in the
rotary rack as well as in horizontal channels
has been done.
As research purpose, silicon mono-
crystals have been irradiated at the central
neutron trap of the reactor. Irradiated products
of good quality, appropriate for fabrication of
power diodes and thyristors have been created
thanks to proper neutron distribution in this
irradiation facility and suitable cadmium ratio.
- Reactor engineering for nuclear power
programme;
- Research and development activities;
- State management in the field;
- And University lecturer training program.
7
RESULTS OF OPERATION AND UTILIZATION OF THE DALAT NUCLEAR RESEARCH REACTOR
IV. SOME MAIN REACTOR RENOVATION
PROJECTS PERFORMED
B. Reactor control and instrumentation system
modification
A. Reactor conversion from HEU to LEU fuels
The Control and Instrumentation System
(C&I) of the DNRR was designed and
manufactured by the former Soviet Union and
put into operation in November 1983. Due to
the spare part procurement problem was
suspected and using technology of the 1970’s
with discrete and low-level integrated
electronic components, the system technology
was somewhat obsolete and un-adapted to
tropical climate.
In the framework of the program on
Russian Research Reactor Fuel Return
(RRRFR) and the program on Reduced
Enrichment for Research and Test Reactor
(RERTR), the DNRR core was partly
converted from HEU to LEU in September
2007.
After this success, the full core
conversion study from HEU to LEU of the
DNRR was also carried out during years 2008
- 2010. The results of neutronics, thermal
hydraulics and safety analysis showed that a
LEU core loaded with 92 fuel assemblies and
12 beryllium rods around the neutron trap
satisfies the safety requirements while
maintaining the utilization possibility similar
to that of the previous HEU and recent mixed
fuel cores.
The first renovation work was
implemented during 1992-1993 period and the
renovated C&I system was commissioned at
the end of 1993. The most important
renovation task was to redesign and construct a
number of electronic systems/blocks, which
play the key role in enhancing the reliability of
the system. This renovation work was focused
mainly on the process and instrumentation
system, but not on the neutron measurement
and data processing parts. Because of that, it
was necessary to fulfill the second renovation
and modernization during the years of 2005-
2007 to replace neutron measurement and
signal processing parts of the existing C&I
system by the digital system named ASUZ-
14R. The main items replaced under the
second modification are neutron detector
channels; neutron flux control system
(NFCS), reactor protection system, control
console and control panels, reactor protocol
and diagnostic system, etc.
Physics and energy start-up of the
DNRR for full core conversion to low
enriched uranium (LEU) fuel were performed
from November 24th, 2011 until January 13th,
2012 according to a planned program that
was approved by Vietnam Atomic Energy
Institute (VINATOM). At 15:35 on
November, 30th, 2011 the reactor reached
criticality with core configuration including
72 LEU FAs and neutron trap in center. Then
the fuel loading for working core and power
ascension test were also carried out from
December, 6th, 2011 to January, 13th, 2012.
Experimental results of physical and thermal
hydraulics parameters of the reactor during
start up stages and long operation cycles at
nominal power showed very good agreement
with calculated results and met the safety
requirements.
The commissioning of the new I&C
system was finished in August 2007 and
operating license was approved in October
2007.
8
NGUYEN NHI DIEN et al.
V. CONCLUSIONS
REFERENCES
The DNRR has been safely operated and
effectively utilized for 30 years. To achieve
that, maintaining and upgrading the reactor
technological facilities have been done with a
high quality. The reactor physics and thermal
hydraulics studies have also provided the
important bases for safety evaluation and in-
core fuel management to ensure its safe
operation and effective exploitation. The
safety and security for the reactor are one of
the main issues that national and local
authorities are particularly interested in and
strongly support up.
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Reactor - Twenty five years of safe operation
and efficient exploitation, Dalat, (March 2009).
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Topical Meeting on Research Reactor Fuel
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During 30 years of operation, the DNRR
has been playing an important role in the use
of atomic energy for peaceful purpose in
Vietnam. The reactor has been used for
radioisotope production for medicine and
industry purposes, NAA of geological, crude
oil and environment samples, performance of
fundamental and applied researches on
nuclear and reactor physics, as well as
creation of a large amount of human resource
with high skills and experiences on
application of nuclear techniques in the
country. A strategic plan and long-term
working plan for the DNRR has been set up in
order to continue its safe operation and
effective utilization at least to 2025.
[5] P.V. Lam, N.N. Dien, L.V. Vinh, H.T.
Nghiem, L.B. Vien and N.K. Cuong,
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It should be mentioned that a project for
establishment of a new nuclear science and
technology center with a high power research
reactor expected to put into operation between
2020-2022 is now under preparation and
consideration. Therefore, the DNRR will be
necessary and keep playing an important role
in scientific research, applications and human
resource development for Vietnam in the
coming time.
[8] N.N. Dien, L.B. Vien, P.V. Lam, L.V. Vinh,
H.T. Nghiem, N.K. Cuong, N.M. Tuan, N.M.
Hung, P.Q. Huy, T. Q. Duong, V.D.H. Dang,
T.C. Su, T.T. Vien, Some main results of
commissioning of the Dalat Nuclear Research
Reactor with low enriched fuel, Nuclear
Research Institute, (2012).
[9] Safety Analysis Report (SAR) for the Dalat
Research Reactor, Dalat, (2012).
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